Annual average Secchi disk depth measurements recorded at the Lake Tahoe Index Station (1968 through 2017). Each annual value is an integrated average using 18 to 37 individual measurements taken throughout the year. The trend line (dashed line) is determined statistically using a general additive model (GAM). The five-year running average (red line) between 2012 and 2017 was 21.3 meters (70 feet), 2.5m less than the TMDL Clarity Challenge target of 23.8 meters (78 feet) by 2026. Data from the UC Davis – Tahoe Environmental Research Center.
Transparency of Lake Tahoe as measured by the annual average Secchi depth.